Cathode ray tube having standby cathode assembly on rotatable support

ABSTRACT

Apparatus for use in cathode ray tubes and particularly in multi-gun color television picture tubes and like devices to enable substituting for the active cathodes and associated parts other standby cathodes and parts which will restore the tube to full emissive power and substantially double the life of the tube, said apparatus including a multicathode assembly mounted inside the neck portion of the envelope of the picture tube, said assembly having a plurality of active and standby cathodes and associated heater elements mounted thereon, and means including magnetic means for moving said assembly between alternate positions inside the tube envelope whereby selected ones of the cathodes and their associated heater elements are in operative positions and others are not. The present apparatus enables replacement of the active cathodes without requiring any modification of the tube envelope itself, without requiring removal of the tube from the set in which it is installed, and with little or no modification or adjustment of the set to accommodate the change.

United States Patent Leonard [451 'July18,1972

[ CATHODE RAY TUBE HAVING STANDBY CATHODE ASSEMBLY ON ROTATABLE SUPPORT [72] Inventor: James L. Leonard, 102 Archer Drive,

Godfrey, 111. 62035 [22] Filed: June 17, 1970 21 Appl. No.: 47,002

FOREIGN PATENTS OR APPLICATIONS 697,823 9/1953 Great Britain ..3l3/237 '0 \HH out 64 Primary Examiner-Robert Segal Attorney-Charles B. Haverstock 57 ABSTRACT Apparatus for use in cathode ray tubes and particularly in multi-gun color television picture tubes and like devices to enable substituting for the active cathodes and associated parts other standby cathodes and parts which will restore the tube to full emissive power and substantially double the life of the tube, said apparatus including a multicathode assembly mounted inside the neck portion of the envelope of the picture tube, said assembly having a plurality of active and standby cathodes and associated heater elements mounted thereon, and means including magnetic means for moving said assembly between alternate positions inside the tube envelope whereby selected ones of the cathodes and their associated heater elements are in operative positions and others are not. The present apparatus enables replacement of the active cathodes without requiring any modification of the tube envelope itself, without requiring removal of the tube from the set in which it is installed, and with little or no modification or adjustment of the set to accommodate the change.

14 Claims, 8 Drawing Figures CATIIODE RAY TUBE HAVING STANDBY CATIIODE ASSEMBLY ON ROTATABLE SUPPORT Various means and methods have been devised for restoring television picture tubes and other similar devices including particularly color television picture tubes to a new or near new condition after they have been in service for extended periods. The known means and methods have included modifying or opening the tube envelope to enable physical replacement of one or more cathodes and/or their associated heater elements. Other known means have included adding components to the set to increase the voltage and/or current applied to the existing heater elements to increase the temperature and hence the cathode emission as the emission falls off with tube age, and various mechanical devices have been used which are mounted on and extend through the sealed tube envelopes to enable moving or relocating certain parts inside the tubes, hopefully without destroying the sealed condition that exists. All of the known means and methods have been relatively complicated and expensive and have altered or modified the construction, size and other physical characteristics of the tube and/or the set in which the tube is installed and the known means and methods for the most part require special tools and/or special extra parts which further complicate matters and add to the cost and time required to make the change. Also, the known means for installing standby cathodes are difficult and time consuming to install in the limited space available inside the neck portion of a cathode ray tube and for these and other reasons the known devices have been unsatisfactory and have not received wide acceptance and usage.

The present device overcomes these and other disadvantages and shortcomings of the known prior art devices and methods by teaching the construction and operation of relatively inexpensive means, totally contained within the envelope of the cathode ray tube, and yet which provide means by which standby, unused cathodes and associated heaters can be substituted for those that have been in use for some time and are damaged or areshowing signs of wear and loss of emission. The present invention provides the means for accomplishing this without requiring that the tube envelope be modified or that its sealed condition be endangered, and without requiring that the tube be removed from the set. Furthermore, replacement or substitution of one set of cathodes for another using the subject means can be performed by persons having relatively little skill and training, in a minimum amount of time, with a high degree of accuracy, and as stated, without removing the tube from the set in which it is installed, and with little or no adjustment or alignment being required. The present construction also includes means for protecting the standby cathodes and heater elements from deterioration caused by the heat and radiation incident to normal operation of the tube.

It is therefore a principal object of the present invention to provide improved means for substituting standby cathodes and associated heater elements in a cathode ray tube, and particularly in a multi-cathode color television picture tube or similar device to restore the tube to a substantial new operating condition.

Another object is to substantially double the operating life of cathode ray tubes and like devices.

Another object is to provide relatively simple and inexpensive means by which the emission characteristics of cathode ray tubes and like devices can be restored to a substantially new operating condition.

Another object is to provide means by which the cathodes in color television picture tubes can be replaced by standby cathodes without removing the tube from the set.

Another object is to provide means for making a substitution of the active cathodes in color television picture tubes without effecting or destroying the sealed closed condition of the tube or changing or modifying the envelope of the tube.

Another object is to minimize possible deterioration to replacement cathodes which are mounted in the envelope of operating cathode ray tubes due to the heat and radiation generated during operation thereof.

Another object is to replace the operating cathodes in a sealed envelope by the use of magnetic coupling means.

Another object is to make it possible to restore a picture tube to a substantially new operating condition without upsetting the alignment and other set adjustments.

Another object is to enable replacement of the active cathodes and associated components in a television picture tube without requiring adding any parts to the tube or set in the field.

These and other objects and advantages of the present invention will become apparent to those skilled in the an after considering the present disclosure which shows and describes several embodiments of the subject invention in conjunction with the accompanying drawing, wherein:

FIG. 1 is a side elevational view of a color television picture tube having means therein for replacing the active cathode assemblies constructed according to the present invention;

FIG. 2 is an enlarged cross-sectional view taken through the rear neck portion of the tube of FIG. 1;

FIG. 3 is a fragmentary cross-sectional view similar to FIG. 2 but showing the movable cathode assembly in a rearwardly moved position during substitution of standby cathode assemblies for those cathode assemblies that have been in operation;

FIG. 4 is a view taken on line 4-4 of FIG. 3;

FIG. 5 is a further enlarged fragmentary cross-sectional view showing even more of the details of the movable cathode assembly and related parts;

FIG. 6 is a cross-sectional view taken on line 6-6 of FIG. 2;

FIG. 7 is a cross-sectional view similar to FIG. 6 but showing the movable cathode assembly in its alternate operating position; and,

FIG. 8 is a cross-sectional view taken on line 8-8 of FIG. 3.

Referring to the drawing more particularly by reference number, number 10 refers to a cathode ray tube and more particularly to a multi-gun color television picture tube. The overall construction of the tube 10 may be similar to a conventional television picture tube including having an enlarged forward portion 12 which includes a viewing surface 14 on which the images to be'observed are produced. The tube 10 also includes a neck portion 16 in which the electron guns and other operating portions of the tubes are located. The entire tube 10 including the portions l2, l4 and 16 is formed as a sealed glass envelope 17 or the like which is evacuated in the usual manner. The subject improvements are mounted in the rear end of the neck portion 16 of the tube envelope l7 and reside mainly in a movable cathode assembly 18 and a cooperating stationary grid assembly 20 which is positioned adjacent thereto. The stationary grid assembly 20 includes a round disc member 22 formed of a dielectric substance such as porcelain, ceramic, or other substance capable of withstanding the relative high temperatures without being damaged and without giving off gases which might contaminate the tube environment. The disc 22 is connected to the forward end of a dielectric shaft or rod 24 which extends rearwardly therefrom inside of the tube envelope and has its opposite rear end fixedly attached to the rear wall 26 of the tube envelope. The disc 22 in a typical three gun color television picture tube has positions thereon for three similar cup-shaped grid elements 28 which are mounted in holes located in the disc at l20 intervals therearound. Each of the cup-shaped grids 28 has a centrally located orifice or hole 30 through which electrons emitted by an associated cathode move as they are accelerated through the associated gun assembly toward the inner surface of the forward tube wall 14. The gun assemblies, of which there are three in a color picture tube, may be of a usual conventional construction and are identified generally in FIG. 2 by the number 32.

The stationary disc 22 also has three other equally spaced holes or pockets 34 formed therein at intervals and located in the spaces between the cup-shaped grid members 28. The holes or pockets 34 are preferably closed on their forward ends by wall means 36 and the holes 34 including the walls 36 are provided to accommodate three cathode assemblies, namely the standby cathode assemblies as will be explained later. The holes 34 and the associated walls 36 may be coated or lined with radiation and/or heat insulating substances identified by 37 in FIG. to prevent the standby cathodes positioned therein from being as exposed to the heat and radiation generated inside the tube envelope 17 during operation of the active cathodes which are the cathodes positioned in alignment with the respective grid members 28.

The present invention resides mainly in the movable cathode assembly 18, which assembly includes another dielectric disc 38 with a central opening 40 that is large enough to freely receive and permit movement thereof along the shaft 24. The disc 38 has six equally spaced holes 42 located at 60 intervals therearound and in positions to be aligned with the holes 34 and the grid members 28. Each of the holes 42 has a cathode assembly mounted in it. A cathode assembly includes a cup-shaped cathode member 44 with a forwardly facing surface 46 coated with a substance capable of emitting electrons when heated to a desired temperature. One of the cathode members 44 is positioned in each of the holes 42 and each of the cathodes has its own heater element such as the heater coil 48 positioned extending into it from the rear as shown.

The disc 38 also has two or more metal members 50 and 52 attached to its periphery on opposite sides thereof as shown. The members 50 and 52 are constructed of steel, iron or some other magnetizeable substance and are positioned adjacent to but not in contact with the inner surface of the neck portion 16 of the tube envelope. The purpose for the members 50 and 52 is important to the present invention and will be described later.

A coil spring 54 is positioned on the shaft 24 and extends from between the rear envelope wall 26 and the movable disc 38 to bias the cathode assembly 18 into a forwardly extending position which is the position shown in FIG. 2 of the drawing. In the forwardly extending position of the assembly 18, three of the cathode members 44 extend into respective ones of the three spaced cup-shaped grid members 28 and the other three cathode members 44 extend into respective ones of the -openings 34 in the stationary disc member 22. The three cathodes which extend into the grid members 28 are the active cathodes and their associated heater elements 48 are connected either in series or parallel as desired and to particular pins 56 which are part of a male socket assembly 58 or other suitable connection means attached to the rear end of the neck portion 16 of the tube 10. The other three cathodes 44, which are the standby cathodes in this position of the assembly 18 are connected electrically to the adjacent respective active cathodes which they will replace. It is also possible and contemplated to have separate pin connections for each of the sets of cathodes so that adjacent cathodes are not so connected. These standby cathodes have their associated heater elements 48 similarly connected as required but to a difierent combination of the socket pins 56. All of the six cathodes including their heaters 48 on the assembly 18 are movable simultaneously from the positions just described to alternate positions in which the active cathodes become the standby cathodes and the standby cathodes become the active cathodes. This may necessitate a minor change in the power connections to the female socket assembly (not shown) which mates with the male portion 58 so that only the heaters associated with the active cathodes will be energized.

In order to move the movable cathode assembly 18 from a position in which one set of three cathodes 44 are positioned in the respective grids 28 to a position in which the other set are positioned in the grids 28, a magnet member 60 which may be a permanent or an electro-magnet is positioned as shown in FIG. 3 with the pole portions 60A and 60B of the magnet located closely adjacent to the metal members 50 and 52. In this position, the magnet 60 straddles the neck portion 16 of the tube. In order to change active cathodes the magnet 60 is moved rearwardly along the tube neck 16 during which time the magnetic coupling between the magnet 60 and the members 50 and 52 will cause the assembly 18 to move rearwardly inside the tube in opposition to the force of the spring 54. This movement is continued until the assembly 18 has moved to the position shown in FIG. 3 in which the cathodes 44 are clear of the disc 22. Thereafter, while the cathode assembly 18 is in its rearward position, the magnet 60 is rotated through an angular displacement of about 60 which in turn rotates the assembly 18 through a similar angular displacement. This aligns the standby cathodes 44 with the cup-shaped grid members 28 and the active cathodes with the holes 34. In other words, a change has taken place between the positions of the active and standby cathodes. The magnet 60 is now moved forwardly along the neck 16 of the tube to seat and properly position the cathodes in their newly acquired positions to restore the tube to an operating condition. The spring 54 helps to accomplish this and also assures that the cathode assembly 18 will remain in its operating position after it has been moved and after the magnet 60 has been removed. The movable assembly and/or the tube envelope itself or the stationary parts may include cooperating marks such as color coded dots 61 or the like to indicate to the scrviceman or other person which ofthc sets of cathodes and filaments are the active ones.

The stationary disc 22 may have one or more notches, shown as V-shaped notches 62, formed in its rear surface which cooperate with similarly shaped teeth 64 in the movable disc 38 to properly finally orient and align the cathodes in each operating position thereof. The stationary disc 22 is also shown having a rearwardly extending tab 66 (FIGS. 2, 3, 4, 6 and 7) attached near its periphery for cooperating with an arcuate shaped cutout 68 formed in the outer edge of the movable disc 38. The cooperation between the tab 66 and the eutout 68 restricts the amount of possible angular movement of the movable assembly 18 and prevents the operator from moving the movable disc 38 more than 60 in either direction. This is important because it minimizes the possibility of crossing or shorting the leads which connect the heater elements 48 to the socket pins 56 and it also minimizes the necessary length of these leads. It should also be apparent that the position of the notches 62 and teeth 64 as well as the positions of the tab 66 and cutout 68 can be reversed on the discs 22 and 38, if desired.

The connections from the heater elements 48 to the pins 56 can be made in several different ways. Probably the simplest is to have one side or one connection to each of the six heater elements connected to a common pin on the socket assembly 58, and have the other connections to each set of alternate heaters, be the heaters connected in series or parallel, connected to other socket pins 56. With this arrangement only three pins are required to connect all of the heaters to the socket pins. It is then simply a matter of selecting between two pins to control which of the heaters are to be activated. This can be done quickly and simply by reversing or changing two connections on the female adapter or plug which mates with the male adapter 58 and is the only electrical change ordinarily required when changing from one set of three cathodes to the other set.

FIGS. 6 and 7 show the two alternate operating positions of the assembly 18. In FIG. 6 the two metal members 50 and 52 are shown vertically oriented and the tab 66 is shown located near the upper end of the cutout 68. In FIG. 7 the metal members 50 and 52 are shown moved counter-clockwise through an angle of 60, and the cutout 68 which for illustrative purposes is shown on the movable instead of on the stationary disc has been moved through an angle of 60 so that the tab 66 is now located near to the opposite end of the cutout 68.

It can thus be seen that with the subject movable assembly 18 the useable life of the cathode ray tube 10 can be substantially doubled and this can be accomplished without removing the tube from the television or other set in which it is installed and without requiring any substantial circuit changes or modifications or any readjustment or realignment. The subject change can also be performed with little or no likelihood that the tube and its contents will be damaged and without adding any parts or making any changes to the set itself. Furthermore, and importantly, the subject means enable replacement of the cathodes without modifying or installing anything in the envelope of the tube which might cause a leak or loss of operating environment. This is possible because with the present means the only thing that enters the tube to make the cathode switch is a magnetic field. After a cathode change has been made, it may be necessary, however, to deGauss the tube to restore it to its proper operating condition, but this is often necessary anyway when the set is being serviced and involves a routine procedure requiring no special tools or other equipment.

Thus, there has been shown and described novel means for substituting or replacing the cathodes which have been in use and are weak or otherwise unacceptable in a color television picture tube with other standby cathodes in order to restore full emission characteristics to the tube and make the tube operate in a substantially new condition, which means fulfill all of the objects and advantages sought therefor. Many changes, modifications, variations, and other uses and applications of the subject means in addition to use in color television picture tubes can also be made of the present invention without departing from the spirit and scope of the invention. All such changes, modifications, variations and other uses and applications thereof which do not depart from the spirit and scope of the invention are deemed to be covered by the invention which is limited only by the claims which follow.

What is claimed is:

1. In a color television picture tube having an envelope including a neck portion with three electron gun assemblies positioned therein each having an associated grid, cathode and cathode heater means, the improvement comprising means forming a standby cathode and associated cathode heater for each of the gun assemblies, means for supporting all of said cathodes including the standby cathodes, said cathode support means having at least one portion thereof formed of a magnetizeable material, magnet means movable adjacent to the neck portion of the tube envelope in position to be magnetically coupled to the magnetizeable portion of said cathode support means, and means in said tube envelope permitting limited movement of said cathode support means and the cathodes supported thereon under control of movement of the magnet means between a first position in which the standby cathodes are out of alignment with the associated grids and a second position in which the standby cathodes are respectively aligned with said grids.

2. In the color television picture tube defined in claim 1 means biasing said cathode support means in a direction to maintain it in said first or second position.

3. In the color television picture tube defined in claim 1 means for shielding the standby cathodes in the first position of said cathode support means.

4. In the color television picture tube defined in claim 3 said shielding means include means for shielding said standby cathodes from the operating heat generated in the tube.

5. In the color television picture tube defined in claim 3, said shielding means include means to shield the standby cathodes from radiations generated in the tube.

6. In the color television picture tube defined in claim I, said means permitting limited movement of the cathode support means include means to limit movement thereof to an angular displacement of approximately 60.

7. In the color television picture tube defined in claim 1 separate electrical connections are provided in the tube to the heater means associated with the standby cathodes.

8. In the color television picture tube defined in claim 1 means are provided to accurately locate the cathode support means and the cathodes mounted thereon in the said first and said second positions thereof.

9. Means for restoring the emission characteristics of a multi-gun cathode ray tube to a substantially new emission condition comprising a multi-gun cathode ray tube, each gun having a stationary grid and an associated aligned cathode assembly, means forming a standby cathode assembly associated with each of said aligned cathode assemblies, a movable disclike member locate Inside the cathode ray tube for supporting the aligned and the standby cathode assemblies, means mounting said movable disc-like member for limited axial and rotational movement inside the tube, and means for moving said movable disc-like member including the aligned and the standby cathode assemblies supported thereon between a first position in which the aligned cathodes are in alignment with the respective stationary grids and a second position in which the standby cathode assemblies are aligned with said respec tive stationary grids, said moving means including means on the movable member capable of being magnetically coupled to magnetic means located externally of the cathode ray tube and means for maintaining the movable member in the last of said first and second positions in which it is positioned.

10. The means for restoring the emission characteristics of a multi-gun cathode ray tube defined in claim 9 wherein said aligned and standby cathode assemblies are arranged on said disc-like member in equi-angular spaced relationship such that the aligned cathode assemblies alternate with the standby cathode assemblies.

11. The means for restoring the emission characteristics of a multi-gun cathode ray tube defined in claim 9 including a first set of aligned cathode assemblies and a second set of standby cathode assemblies, said aligned and standby sets of cathode assemblies exchanging places with each other when the mova ble member is moved between the said first and second positions thereof, and means for shielding one set of said cathode assemblies in each position of the movable member.

12. In a cathode ray tube having an envelope including a neck portion with an electron gun assembly positioned therein, said gun assembly including a grid, an operative cathode and cathode heater means, the improvement comprising a standby cathode positioned in lateral spaced relationship to the operative cathode in the neck portion of the tube, disc-like common means for supporting the operative and the standby cathodes, said common disc-like cathode support means including a member mounted inside the neck portion of the tube envelope and movable therein between a first position in which the operative cathode is positioned in alignment with the grid of said electron gun assembly, and a second position in which the standby cathode is in alignment with the grid of the said gun assembly, means mounting said disc-like support means for limited axial and rotational movement in the neck portion of the tube, said cathode disc-like support means having a magnetizeable portion thereof that is positioned adjacent to the neck portion of the tube envelope, and means external of the tube for magnetically coupling with the said magnetizeable portion of the cathode disc-like support means through the envelope of the tube, said cathode disc-like support means being movable inside the tube envelope when magnetically coupled in response to predetermined movements of the magnetic coupling means between the said first and said second positions thereof and means to maintain the disc-like support means in the last of said first and second positions in which it is positioned.

13. In the cathode ray tube defined in claim 12 including means for shielding the standby cathode in the first position of the cathode support means.

14. In the cathode ray tube defined in claim 12 including cooperating indicator means to indicate whether the said common cathode disc-like support means are in the first or second position thereof. 

1. In a color television picture tube having an envelope including a neck portion with three electron gun assemblies positioned therein each having an associated grid, cathode and cathode heater means, the improvement comprising means forming a standby cathode and associated cathode heater for each of the gun assemblies, means for supporting all of said cathodes including the standby cathodes, said cathode support means having at least one portion thereof formed of a magnetizeable material, magnet means movable adjacent to the neck portion of the tube envelope in position to be magnetically coupled to the magnetizeable portion of said cathode support means, and means in said tube envelope permitting limited movement of said cathode support means and the cathodes supported thereon under control of movement of the magnet means between a first position in which the standby cathodes are out of alignment with the associated grids and a second position in which the standby cathodes are respectively aligned with said grids.
 2. In the color television picture tube defined in claim 1 means biasing said cathode support means in a direction to maintain it in said first or second position.
 3. In the color television picture tube defined in claim 1 means for shielding the standby cathodes in the first position of said cathode support means.
 4. In the color television picture tube defined in claim 3 said shielding means include means for shielding said standby cathodes from the operating heat generated in the tube.
 5. In the color television picture tube defined in claim 3, said shielding means include means to shield the standby cathodes from radiations generated in the tube.
 6. In the color television picture tube defined in claim 1, said means permitting limited movement of the cathode support means include means to limit movement thereof to an angular displacement of approximately 60*.
 7. In the color television picture tube defined in claim 1 separate electrical connections are provided in the tube to the heater means associated with the standby cathodes.
 8. In the color television picture tube defined in claim 1 means are provided to accurately locate the cathode support means and the cathodes mounted thereon in the said first and said second positions thereof.
 9. Means for restoring the emission characteristics of a multi-gun cathode ray tube to a substantially new emission condition comprising a multi-gun cathode ray tube, each gun having a stationary grid and an associated aligned cathode assembly, means forming a standby cathode assembly associated with each of said aligned cathode assemblies, a movable disc-like member located inside the cathode ray tube for supporting the aligned and the standby cathode assemblies, means mounting said movable disc-like member for limited axial and rotational movement inside the tube, and means for moving said movable disc-like member including the aligned and the standby cathode assemblies supported thereon between a first position in which the aligned cathodes are in alignment with the respective stationary grids and a second position in which the standby cathode assemblies are aligned with said respective stationary grids, said moving means including means on the movable member capable of being magnetically coupled to magnetic means located externally of the cathode ray tube and means for maintaining the movable member in the last of said first and second positions in which it is positioned.
 10. The means for restoring the emission characteristics of a multi-gun cathode ray tube defined in claim 9 wherein said aligned and standby cathode assemblies are arranged on said disc-like member in equi-angular spaced relationship such that the aligned cathode assemblies alternate with the standby cathode assemblies.
 11. The means for restoring the emission characteristics of a multi-gun cathode ray tube defined in claim 9 including a first set of aligned cathode assemblies and a second set of standby cathode assemblies, said aligned and standby sets of cathode assemblies exchanging places with each other when the movable member is moved between the said first and second positions thereof, and means for shielding one set of said cathode assemblies in each position of the movable member.
 12. In a cathode ray tube having an envelope including a neck portion with an electron gun assembly positioned therein, said gun assembly including a grid, an operative cathode and cathode heater means, the improvement comprising a standby cathode positioned in lateral spaced relationship to the operative cathode in the neck portion of the tube, disc-like common means for supporting the operative and the standby cathodes, said common disc-like cathode support means including a member mounted inside the neck portion of the tube envelope and movable therein between a first position in which the operative cathode is positioned in alignment with the grid of said electron gun assembly, and a second position in which the standby cathode is in alignment with the grid of the said gun assembly, means mounting said disc-like support means for limited axial and rotational movement in the neck portion of the tube, said cathode disc-like support means having a magnetizeable portion thereof that is positioned adjacent to the neck portion of the tube envelope, and means external of the tube for magnetically coupling with the said magnetizeable portion of the cathode disc-like support means through the envelope of the tube, said cathode disc-like support means being movable inside the tube envelope when magnetically coupled in response to predetermined movements of the magnetic coupling means between the said first and said second positions thereof and means to maintain the disc-like support means in the last of said first and second positions in which it is positioned.
 13. In the cathode ray tube defined in claim 12 including means for shielding the standby cathode in the first position of the cathode support means.
 14. In the cathode ray tube defined in claim 12 including cooperating indicator means to indicate whether the said common cathode disc-like support means are in the first or second position thereof. 